Inductor current reconstruction

Abstract

In the parallel operation of power supply units, a high line ripple current may be observed in output when the power supply units (PSUs) are supplied with different inputs. For example, a high line ripple current may be observed when PSUs were supplied with different line frequency inputs and/or when PSUs were supplied with different phase angle input lines. A low pass filter is in a control loop which is capable of filtering the line frequency to get an average current reference signal. The average current reference signal is compared with the real time output current to generate an error signal. This error signal is fed back to a voltage control loop to adjust the output in order to compensate the line ripple.

What is claimed is: 
     
       1. A switched-mode power supply, comprising:
 a primary inductor to carry a first varying current in response to a controlled switching device; 
 a secondary inductor electromagnetically coupled with the primary inductor to carry a second varying current that is substantially less than the first varying current and to produce a first varying voltage that is substantially proportional to the first varying current; 
 a current sense element to produce a second varying voltage that is proportional to a low frequency varying current being supplied to a load of the switched-mode power supply; and, 
 control circuitry to receive the second varying voltage and the first varying voltage and to, based on the second varying voltage and the first varying voltage, control the controlled switching device. 
 
     
     
       2. The switched-mode power supply of  claim 1 , wherein the control circuitry further comprises:
 a summation circuit to combine the second varying voltage with the first varying voltage to produce a varying feedback voltage. 
 
     
     
       3. The switched-mode power supply of  claim 1 , wherein the control circuitry executes firmware that combines a second varying voltage indicator with a first varying voltage indicator to produce a varying feedback indicator. 
     
     
       4. The switched-mode power supply of  claim 1 , wherein the primary inductor and the controlled switching device are arranged in a buck converter topology. 
     
     
       5. The switched-mode power supply of  claim 1 , wherein the primary inductor and the controlled switching device are arranged in a boost converter topology. 
     
     
       6. The switched-mode power supply of  claim 2 , wherein the summation circuit is implemented using analog circuitry. 
     
     
       7. The switched-mode power supply of  claim 1 , wherein the secondary inductor is electromagnetically coupled with the primary inductor using a primary inductor to secondary inductor turns ration of more than ten (10). 
     
     
       8. A method of controlling a switched-mode power supply, comprising:
 using a controlled switching device, inducing a primary inductor to carry a first varying current; 
 electromagnetically coupling the primary inductor with a secondary inductor to induce a second varying current that is substantially less than the first varying current in the secondary inductor and to induce the secondary inductor to produce a first varying voltage that is substantially proportional to the first varying current; 
 sensing a second varying voltage that is proportional to a low frequency varying current being supplied to a load of the switched-mode power supply; and, 
 based on the second varying voltage and the first varying voltage, controlling the controlled switching device. 
 
     
     
       9. The method of  claim 8 , further comprising:
 summing the second varying voltage with the first varying voltage to produce a varying feedback voltage. 
 
     
     
       10. The method of  claim 8 , wherein control circuitry executes firmware that sums a second varying voltage indicator with a first varying voltage indicator to produce a varying feedback indicator. 
     
     
       11. The method of  claim 8 , wherein the primary inductor and the controlled switching device are arranged in a buck converter topology. 
     
     
       12. The method of  claim 8 , wherein the primary inductor and the controlled switching device are arranged in a boost converter topology. 
     
     
       13. The method of  claim 9 , wherein summing the second varying voltage with the first varying voltage is performed using analog circuitry. 
     
     
       14. The method of  claim 8 , wherein the secondary inductor is electromagnetically coupled with the primary inductor using a primary inductor to secondary inductor turns ration of more than ten (10). 
     
     
       15. A switched-mode power supply, comprising:
 a transformer having a primary winding and a secondary winding, the secondary winding configured to produce a first varying voltage that is substantially proportional to a varying current flowing in the primary winding; 
 a current sense element to produce a second varying voltage that is proportional to a low frequency varying current being supplied to a load of the switched-mode power supply; and, 
 control circuitry configured to receive a first varying voltage and a second varying voltage and to, based on the first varying voltage and the second varying voltage, control a switching device that induces current changes in the primary winding. 
 
     
     
       16. The switched-mode power supply of  claim 15 , wherein the control circuitry further comprises:
 a summation circuit to combine the second varying voltage with the first varying voltage to produce a varying feedback voltage. 
 
     
     
       17. The switched-mode power supply of  claim 15 , wherein the control circuitry executes firmware that combines a second varying voltage indicator with a first varying voltage indicator to produce a varying feedback indicator. 
     
     
       18. The switched-mode power supply of  claim 15 , wherein the primary winding and the controlled switching device are arranged in a buck converter topology. 
     
     
       19. The switched-mode power supply of  claim 15 , wherein the primary winding and the controlled switching device are arranged in a boost converter topology. 
     
     
       20. The switched-mode power supply of  claim 16 , wherein the summation circuit is implemented using analog circuitry.